The RONSARD Radars: Internal Calibration Techniques Using Coherent and Noise Sources

The methods for calibrating each meteorological radar of the RONSARD system are described in this paper. The special procedures used have their origin in the complexity of the equipment. The internal calibration of the receiver chain, which is the first step of the overall radar calibration, is described first. The complex structure of the receiver is analyzed and each element replaced by an equivalent circuit, thus yielding a reduced block diagram of the receiver chain. This diagram is then used to determine the receiver gain as a function of the receiver parameters. Special attention is given to the behavior of the receiver adapted filter (preintegrator) and to that of the hard-wired Fourier transformer when processing various types of signal spectra. Three measurements of the receiver gain are finally carried out using calibrated sources (coherent RF source, 10 600 K noise source, and internal radar noise). The results exhibit a correct stability of the radar constant obtained from independent measurements. The addition of quantization noise in the Fourier transformer is also analyzed and discussed.